diff options
Diffstat (limited to 'tables/fastmath.py')
| -rwxr-xr-x | tables/fastmath.py | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/tables/fastmath.py b/tables/fastmath.py index 202561a..0212e06 100755 --- a/tables/fastmath.py +++ b/tables/fastmath.py @@ -19,25 +19,33 @@ import numpy as np import matplotlib.pyplot as plt -def fast_exp2(x, p): +def fast_exp2(x, t, p): p = p.astype(np.float32) x = x.astype(np.float32) - y = (((((p[0]*x) + p[1])*x + p[2])*x + p[3])*x + p[4])*x + 1 + m = ((x + 0.5/8) % (1/8)) - (0.5/8) + e = int((x - m) * 8) - return np.power(y.astype(np.float32), 16) + y = ((((p[0]*m) + p[1])*m + p[2])*m + p[3])*m + p[4] + y = y * 2**(e // 8) * t[e % 8] + + return y.astype(np.float32) def approx_exp2(): - x = np.arange(-8, 8, step=1e-3) + x = np.arange(0, 1/8, step=1e-6) + p = np.polyfit(x, 2 ** x, 4) + t = [ 2**(i/8) for i in range(8) ] + + x = np.arange(-10, 10, step=1e-3) + y = [ fast_exp2(x[i], t, p) for i in range(len(x)) ] - p = np.polyfit(x, ((2 ** (x/16)) - 1) / x, 4) - y = [ fast_exp2(x[i], p) for i in range(len(x)) ] e = np.abs(y - 2**x) / (2 ** x) - print('{{ {:14.8e}, {:14.8e}, {:14.8e}, {:14.8e}, {:14.8e} }}' - .format(p[0], p[1], p[2], p[3], p[4])) + print('{{ {:14.8e}, {:14.8e}, {:14.8e}, {:14.8e}, \n' + ' {:14.8e}, {:14.8e}, {:14.8e}, {:14.8e}, '.format(*t)) + print('{{ {:14.8e}, {:14.8e}, {:14.8e}, {:14.8e}, {:14.8e} }}'.format(*p)) print('Max relative error: ', np.max(e)) print('Max RMS error: ', np.sqrt(np.mean(e ** 2))) |